QoS Routing in Ad-hoc Networks

Transcription

1 QoS Routing in Ad-hoc Networks Seminar Presentation for Advanced Topics in Broadband Networks Nirmal Mahadevan Balasubramanyam Guruprasad Sudharsan Srinivasan

2 Outline QoS Parameters of QoS Challenges, Design and Classification of QoS Routing Routing Protocols QoS Aware AODV On-demand link-state multipath QoS RP (OLMQR) Asynchronous QoS Routing (AQR) QOLSR QoS Frameworks 2

3 What is QoS? QoS is the performance level of service offered by a network to the user. The Goal of QoS is to achieve a more deterministic network behavior so that the information carried by the network can be better delivered and the resources can be better utilized. QoS routing is the process of providing end to end loop free paths to ensure the necessary QoS parameters are met. 3

4 Parameters of QoS Networks (1) Different services require different QoS parameters. Multimedia Bandwidth, delay jitter & delay Emergency services Network availability Group communications Battery life. 4

5 Parameters of QoS Networks (2) Generally the parameters that are important are: bandwidth delay jitter jitter battery charge processing power buffer space 5

6 Challenges in QoS Routing Dynamically varying network topology Imprecise state information Lack of central coordination Hidden node problem Limited resource Insecure medium 6

7 Design Choices for QoS Support Hard state versus soft state reservation Stateful versus stateless approach Hard QoS versus soft QoS approach 7

8 Classification of QoS Routing Protocols Classification of Qos approches Based on interaction btw routing protocol &Qos provisioning mechanism Based on interaction between network and MAC layers Based on the routing information update mechanism employed coupled Decoupled Independent Dependent Ondemand Table driven Hybrid TBP PLBQR TDR QosAODV OLMQR AQR CEDAR INORA INSIGNIA SWAN PRTMAC TBP PLBQR QosAODV INSIGNIA INORA SWAN TDR BR OQR OLMQR AQR CEDAR PRTMAC TBP TDR QosAODV OQR OLMQR AQR INORA PRTMAC PLBQR BR CEDAR 8

9 Layer wise Classification of QoS Solutions Layer wise Qos solutions MAC/DLL Network layer Qos Framework (cross-layer Cluster TDMA e DBASE MACA/PR RTMAC ON-DEMAND: TBP TDR Qos AODV OQR OLMQR AQR TABLE DRIVEN: PLBQR HYBRID: BR CEDAR INSIGNA INORA SWAN PRTMAC 9

10 Network Layer Solutions The bandwidth reservation and real time traffic support capability of MAC protocols can ensure reservation at the link level only. Network layer solution ensures end to end resource negotiations, reservation & reconfiguration. QoS routing protocol must find paths that consume less resources. 10

11 QoS Metrics There are three QoS routing metrics 1) Additive metric 2) Concave metric 3) Multiplicative metric 11

12 QoS Routing Protocols QoS aware AODV On-Demand Link-State Multipath QoS Routing Protocol Overview of Bandwidth Routing (BR) and On-Demand QoS Routing (OQR) Asynchronous QoS Routing Other reactive approaches QoS extension to OLSR (QOLSR) 12

13 AODV AODV is designed for ad-hoc networks, on demand algorithm, loop-free, self starting & scales to large numbers. Supports unicast & multicast By forming trees composed of multicast group members & intermediate nodes needed to connect the group members multicast mode is supported. Ensure route validity AODV uses sequence numbers AODV uses Route request /Route reply to discover a route. 13

14 QoS Object Extension Encoding of QoS information in the standard format which allows complete flexibility for specification of arbitrary values for various QoS requirements. The standard object format is used as the main part of QoS object extension. The fields of QoS object are Reserved QoS profile NNNNN Non default value QoS parameter fields 14

15 QoS Extension Formats (1) 15

16 QoS Extension Formats (2) 16

17 QoS AODV Protocol (1) Perkins extended the basic AODV to provide QoS support in ad-hoc networks. QoS AODV include Object extension on Route Request (RREQ) and Route Reply (RREP) messages which specifies bandwidth and/or delay parameters during the phase of route discovery. A node becomes a hop on the route only if it can meet the requirements specified in the RREQ. If the Route has been already established and the QoS requirement specified cannot be met no longer the node originates an ICMP QOS_LOST message back to the source. 17

18 QoS AODV Protocol (2) There are also two similar mechanisms for guaranteeing maximum delay and minimum available band width on a path. For delay every time the node receives a RREQ it subtracts from the delay the value carried by RREQ the NODE_TRAVERSAL_TIME (time required by the node to process RREQ). If the result is negative then the packet is discarded. For Bandwidth guaranteeing,the value carried in RREQ is compared to the available link capacity.if the available link capacity is lower the packet is discarded.when the destination node replies with a RREP each node forwarding the RREP compares the bandwidth field in the RREP and its own link capacity and maintains the minimum of 2 in the b/w field of RREP before forwarding the RREP. 18

19 QoS Routing Protocols QoS aware AODV On-Demand Link-State Multipath QoS Routing Protocol Overview of Bandwidth Routing (BR) and On-Demand QoS Routing (OQR) Asynchronous QoS Routing Other reactive approaches QoS extension to OLSR (QOLSR) 19

20 Bandwidth Routing Protocol Only bandwidth is considered as QoS parameter. Goal is to find shortest path satisfying the bandwidth requirement. Consists of End-to-end path bandwidth calculation algorithm to inform source node of available bandwidth to any destination. Bandwidth reservation to reserve sufficient number of slots for the QoS flow. A standby routing algorithm to reestablish the QoS flow in case of path breaks. Provides efficient bandwidth allocation scheme for CDMAover-TDMA-based ad hoc wireless networks. 20

21 On-Demand QoS Routing Protocol An admission control scheme over an on-demand QoS routing (OQR) protocol to guarantee bandwidth for real-time applications. Being on-demand in nature no periodic exchange of control information and maintaining routing tables at each node. Similar to BR protocol, network is time-slotted and bandwidth is the key QoS parameter. Consists of: Route Discovery (QRREQ and QRREP) Bandwidth Reservation Reservation Failure (ReserveFail and NoRoute) Route Maintenance (RouteBroken) 21

22 On-Demand Link-State Multipath QoS RP (1) Searches for multiple paths which collectively satisfy the required QoS. Assumes MAC layer is using the CDMA-over-TDMA chanel model similar to BR and OQR protocols. Works as follows: Source floods QRREQ. Each packet contains path history and link-state information. Destination node collects all link-state information and creates own view of network. Destination sends QRREP on all paths which combined satisfy bandwidth requirements. 22

23 On-Demand Link-State Multipath QoS RP (2) Consists of three phases: Phase 1 is on-demand link-state discovery Source floods a QRREQ towards destination Each packet records path history and all link-state information. Destination may receive many different QRREQ packets from source and builds own view of current network topology. Phase 2 is unipath discovery Higher end-to-end path bandwidth is acquired as compared to hop-by-hop approach. For a given unipath, maximum path bandwidth is determined by constructing a time-slot reservation tree T and a least cost timeslot reservation tree T LCF. 23

24 On-Demand Link-State Multipath QoS RP (3) 24

25 On-Demand Link-State Multipath QoS RP (4) T LCF is obtained from T by sorting child nodes on each level of T in ascending order from left to right by using number of reserved time slots in them. The unipath time-slot reservation algorithm performs depth-firstsearch on T LCF to get reservation pattern having maximum bandwidth. 25

26 On-Demand Link-State Multipath QoS RP (5) Phase 3 is multipath discovery and reply Multiple unipaths considered such that sum fulfills bandwidth requirements. Destination applies the unipath discovery operation to each path to determine maximum achievable path bandwidth on each path. For each accepted path destination updates network state information to reflect current bandwidth availability Along each path a QRREP is sent. 26

27 On-Demand Link-State Multipath QoS RP (6) 27

28 On-Demand Link-State Multipath QoS RP (7) Advantages Bandwidth requirements can be met over multiple paths. Has better average call acceptance rate (ACAR). Disadvantages Overhead of maintaining and repairing paths is very high. 28

29 QoS Routing Protocols QoS aware AODV On-Demand Link-State Multipath QoS Routing Protocol Overview of Bandwidth Routing (BR) and On-Demand QoS Routing (OQR) Asynchronous QoS Routing Other reactive approaches QoS extension to OLSR (QOLSR) 29

30 Asynchronous QoS Routing (1) Protocols like Br, OQR, and OLMQR assume TDMA or CDMA-over-TDMA network model. This requires time synchronization across all nodes. Time synchronization requires periodic exchange of control packets. Changes in topology resulting in partitioning/merging causes synchronization problem Merging of two disjoint networks N1 and N2 with different clocks affects existing real-time calls during the merging process (new network will have a single clock) 30

31 Asynchronous QoS Routing (2) Extension of DSR protocol Provides mechanism to reserve asynchronous end to end bandwidth Avoids the time synchronization problem Works in conjunction with RTMAC protocol Covered in an earlier presentation Three phases Bandwidth Feasibility Test Bandwidth Allocation Bandwidth Reservation 31

32 Asynchronous QoS Routing (3) Bandwidth Feasibility Phase Selection of paths with needed bandwidth. Source sends RouteRequest packets to destination. Intermediate node checks bandwidth availability in link on which it received RouteRequest packet. Forwards the packet if sufficient bandwidth is available else it is dropped. Intermediate nodes append reservation table and a time offset to RouteRequest. On receiving RouteRequest packet destination runs slot allocation algorithm on a selected path by constructing QoS Frame for every link. Waits for some time and gathers RouteRequest packets to choose shortest path with necessary bandwidth. 32

33 Asynchronous QoS Routing (4) Bandwidth Allocation Phase Destination performs bandwidth allocation strategy that assigns free slots to every intermediate link in the chosen path. Information about asynchronous slots assigned at every intermediate link is included in the RouteReply. RouteReply is propagated through the selected path back to source. Slot Allocation Strategies Bandwidth allocation and positioning of slots which influence end-to-end delay and call acceptance rate. Early fit reservation (EFR) Minimum bandwidth-based reservation (MBR) Position-based hybrid reservation (PHR) k-hopcount hybrid routing (k-hhr) 33

34 Asynchronous QoS Routing (5) Bandwidth Reservation Phase Reservation of bandwidth at every link of the path is carried out. Reservation is effected by intermediate nodes with the information carried in the RouteReply packet, in an asynchronous fashion using RTMAC protocol. If reservation is successful RouteReply is forwarded. If designated slot is not free at the time of attempting the reservation, any of the free available slots can be reserved. If it is impossible to reserve bandwidth, RouteReply packet is dropped and control packet sent to the destination releases bandwidth reserved on path from this node to destination. 34

35 Asynchronous QoS Routing (6) Advantages End-to-end bandwidth reservation in asynchronous networks. Plan for delay requirements using slot allocation strategies. Disadvantages Setup time and reconfiguration time are high. Bandwidth efficiency not as high as in a fully synchronized TDMA system. 35

36 QoS Routing Protocols QoS aware AODV On-Demand Link-State Multipath QoS Routing Protocol Overview of Bandwidth Routing (BR) and On-Demand QoS Routing (OQR) Asynchronous QoS Routing Other reactive approaches QoS extension to OLSR (QOLSR) 36

37 Other Approaches (1) Ticket Based Distributed QoS Routing protocol. Basic idea is that source issues certain number of tickets and sends these tickets in probes for finding QoS feasible path. Number of tickets indicates number of paths that can be probed in parallel. Tolerates imprecise state information during QoS route computation (more tickets -> more precise the information). Exhibits good performance when degree of imprecision is high. Probes multiple paths in parallel to find a QoS feasible path. Optimality of a path among several feasible paths is explored. A primary-backup-based fault-tolerant technique is used to reduce service disruption during path breaks. 37

38 Other Approaches (2) 38 Trigger Based On-demand distributed QoS routing protocol for real-time applications. Every node maintains only local neighborhood information. Nodes maintain only active routes to reduce control overhead. On imminent link failure, GPS based location of destination used to reroute queries only to certain node neighbors along active route. Following messages exchange for initiating, maintaining, and terminating a real-time session: Initial Route Discovery Route/Reroute Acknowledgement Alternate route Discovery Route Deactivation

39 Other Approaches (3) Predictive Location-Based Based on the prediction of node locations. Overcomes to some extent problems due to presence of stale routing information. No resource reservation in path from source to destination but QoS-aware admission control performed. Network does its best to support QoS requirements. Uses an update protocol, with two types: Type 1 is a periodic update (each node is aware of complete topology refreshed periodically). Type 2 is an update indicates considerable changes Uses location and delay prediction schemes. 39

40 QoS Routing Protocols QoS aware AODV On-Demand Link-State Multipath QoS Routing Protocol Overview of Bandwidth Routing (BR) and On-Demand QoS Routing (OQR) Asynchronous QoS Routing Other reactive approaches QoS extension to OLSR (QOLSR) 40

41 QOLSR QoS extension to OLSR (Experimental RFC 3626). Well suited to large and dense mobile networks Table driven pro-active protocol. Uses hop-by-hop routing. Each node selects a set of neighbor nodes called multipoint relays (MPR) Optimal routes in terms of number of hops. Only MPR forward control traffic and provide a flooding control mechanism. Only partial link state to be flooded. This is used in OLSR for route calculation. 41

42 OLSR 42

43 QOLSR (1) Maximum bandwidth and minimum delay metrics for OLSR. No additional control messages needed. Neighbor detection: Each node MUST detect the neighbor nodes with which it has a direct and bi-directional link. Each node periodically broadcasts HELLO messages, containing the information about its neighbors and their link status. These HELLO messages are received by all one hop neighbors, but they are not relayed to further nodes. 43

44 QOLSR (2) Neighbor QoS measurement Each node MUST estimate the QoS conditions with its neighbors. This info is broadcast using additional fields of hello message. Allows each node to discover its neighborhood up to 2 hops and the QoS conditions Multipoint relay selection Each node selects its MPR set from among its 1-hop symmetric neighbors. MPR set is selected such that it covers all symmetric strict 2-hop nodes. 44

45 QOLSR (3) MPR set consists of subset of the 1-hop neighbors which provides maximum bandwidth and minimum delay to each 2- hop neighbor. MPRs of a given node are declared in the subsequent HELLOs transmitted by this node, so that the information reaches the MPRs themselves. The MPR set is re-calculated when a change in 1 hop or 2 hop neighbor sets with bi-directional link is detected ; or a change is detected in their QoS conditions. 45

46 QOLSR (4) MPR and QOS conditions information declaration Topology Control extension messages sent by MPRs to declare MPR selector set and QoS conditions. Neighborhood information base consists of information about its neighbors, 2 hop neighbors, MPRs and MPR selectors. Each node also maintains a Topology information base and QoS conditions of the network. It receives this information from the TC messages 46

47 QOLSR (5) Routing table Calculation Each node maintains a routing table. The routing table is built from the information in neighbor set and topology set. Uses the shortest-widest path algorithm to find a path with maximum bandwidth (a widest path) using a variant of Dijkstra routing algorithm. When there is more than one widest path, chooses the one with shortest delay. This routing table is updated when a change is detected in the neighbor set, or the topology set. 47

48 QoS Frameworks Framework : a complete system to provide required QoS. All components co-ordinate to provide required services. Key components of a QoS Framework Service model : Per flow or service class. Flexible model Routing QoS signaling: MRSVP, active and passive agents QoS Medium access control: Call admission control Packet Scheduling 48

49 INSIGNIA (1) Provides adaptive services Supports applications that requires min QoS Base QoS Insignia modules Routing module Admission control Packet forwarding Packet scheduling Medium access control In band signaling In-band signaling Supports fast: Reservation Restoration Adaptation schemes The control information is carried along with the data packets Each data packet contains an optional QoS field known also as INSIGNIA field Can operate at a speed close to packet transmission rate 49

50 INSIGNIA (2) 50

51 QoS Frameworks INORA INSIGNIA in-band signaling and TORA routing protocol. SWAN Distributed network model. Assumes best effort best effort MAC and feedback based control mechanisms. Proactive RTMAC Cross layer framework, with on demand QoS extension to DSR routing protocol and real time MAC. 51

52 References C. Siva Ram Murthy, B.S. Manoj, Ad Hoc Wireless Networks: Architectures and Protocols. ISBN x, Copyright Prentice Hall PTR, Inc., May 24, QOLSR, 00.txt. 52

53 Questions? 53

54 Thank You 54